Based on
this thread. The challenge is to, with a post-1800 POD, have Americans decide that the current system doesn't work and write a completely new constitution, multiple times throughout its history. Technically with the Articles and the 1787 Constitution we've already had two: how do we have more?
Like the French republics, 1-5, not balkanizing, eh? Serial instead of parallel.
Well, theres obviously the constitutional convention route. If one gets called, they might either scrap the old and start afresh, or pass so many and such far reaching ones that it amounts to the same thing.
I think one of the reasons a constitutional convention has never been held is that very fear of them getting carried away. Well, that and the usual amending formula works.